The July 2016 Lake Merced Half Marathon in San Francisco California is a 3 loop course on jogging paths around Lake Merced. Walkers may start early, but are then not officially timed. For the official timed race, runners must maintain a max 15 min pace. This race appears to be an inexpensive, no frills race and doesn't appear to include a medal or shirt. The event can also be found on the California Half Marathons page.
Half Marathon Calendar